Universal joints, sometimes called Cardan joints, are generally provided with seals to protect the trunnion bearing, which bearing is usually embodied as a needle bearing. These seals must function in the presence of highly abrasive contaminants. For example, bearings used in motor vehicles, especially those that operate in dusty environments like construction zones, may be exposed to contaminants that can contaminate the universal joints.
To date inner and outer seals (two separate seal systems) have been used in universal joints. By way of example, reference is made to DE 103 02 069 A1 (family member of US 2006/125189) that shows separate inner and outer seals.
A universal joint of the above-mentioned type is also described in DE 195 42 100 C1. In addition, GB 1 211 753 A; US 2010/0289226 A1; U.S. Pat. No. 4,932,923 A; DE 25 56 769 B1 (family member of U.S. Pat. No. 4,094,517); U.S. Pat. No. 3,377,820 A; 6,601,855 B1; and 3,138,942 A disclose alternate solutions.
It has been found that elastomeric seal lips sometimes do not provide an optimal sealing against water, sand, and mud. Instead, adequate sealing can only be achieved by using an inner seal and an outer seal. This can easily lead to wear on the outer seal lip.
A disadvantage of conventional trunnion bearings, including those in the cited documents, is that they require the construction of a relatively expensive inner seal in order to ensure that penetrating dirt is kept away from the region of the trunnion bearing. Conventional assemblies that use two separate seal systems are thus expensive to manufacture and install.